jwst flies thru artist concept image

Space Telescope

Webb will be the largest, most powerful and complex space telescope ever built and launched into space. It will fundamentally alter our understanding of the universe.

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About Webb:

view of webb's primary and secondary mirror in low light test

The James Webb Space Telescope (sometimes called JWST or Webb) is an orbiting infrared observatory that will complement and extend the discoveries of the Hubble Space Telescope, with longer wavelength coverage and greatly improved sensitivity. The longer wavelengths enable Webb to look much closer to the beginning of time and to hunt for the unobserved formation of the first galaxies, as well as to look inside dust clouds where stars and planetary systems are forming today.

Key Facts:

Premier Observatory
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Webb will be the premier space observatory for astronomers worldwide, extending the tantalizing discoveries of the Hubble Space Telescope. About Compare Webb and Hubble
Largest Telescope in Space
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Webb will be the largest telescope ever placed in space; 100 times more powerful than Hubble. So big it has to fold origami-style to fit in the rocket and will unfold like a "Transformer" in space. Webb And Hubble Folding Mirrors
The First Stars and Galaxies
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With unprecedented infrared sensitivity, it will peer back in time over 13.5 billion years to see the first galaxies born after the Big Bang. Science Themes First Light Mather and BigBang
How Galaxies Assemble
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Webb will help astronomers to compare the faintest, earliest galaxies to today's grand spirals and ellipticals, helping us to understand how galaxies assemble over billions of years. Read More
Birth of Stars & Planetary Systems
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Webb will be able to see right through and into massive clouds of dust that are opaque to visible-light observatories like Hubble, where stars and planetary systems are being born. Read More
Exoplanets
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Webb will tell us more about the atmospheres of extrasolar planets, and perhaps even find the building blocks of life elsewhere in the universe. In addition to other planetary systems, Webb will also study objects within our own Solar System. Read More
Orbit
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Webb will orbit the sun, a million miles away from Earth at the second Lagrange point. (L2 is four times further away than the moon!) Read More
Launch
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Webb will launch in 2021 from French Guiana... (The mission lifetime is 5-10+ years.) Read More
Build, Integration & Test
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Webb has over 1200 skilled scientists, engineers and technicians from 14 countries (and more than 27 US states) building it. (It is a joint NASA/ESA/CSA mission.) The Team Assembly and testing of the mirror and instruments occured at NASA Goddard; view time-lapses of the build/test at GSFC.
Technology Innovations:
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Webb has created spinoff technologies. (Including a new LASIK-like procedure for your eyes!) Read More
Webb vs Hubble vs Spitzer
Webb vs other space telescope
Webb’s 18-segment primary mirror is over 6 times bigger in area than Hubble's and will be ~100x more powerful. (How big is it? 6.5 m in diameter.) It has a secondary mirror nearly as big as Spitzer's primary... (The secondary mirror is 0.74 m in diameter. Spitzer's primary is 0.85 m in diameter.) Read More
Size:
Webb size
Webb is about half the size of a 737 yet less than 8% of the mass of a 737. It will be the biggest telescope ever launched into space. (Webb has a total mass of 6200 kg, the maximum mass of a 737 is 79,010 kg.) Read More
Sunshield and Temperature Extremes
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Thanks to the sunshield, the temperature is roughly 600 degrees Fahrenheit less on the cold, shaded side of the observatory than it is on the hot, sunlit side. Read More
Mirrors
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Webb’s primary mirror has 18 segments that work together as one; they can all be individually adjusted. Its segments have a mass of ~20 kg (44 lbs) each and are 4.3 feet tall. (You could lift one pretty easily.) Requires only about a golf ball's worth of gold coat for the huge primary mirror. (The coating is so thin that a human hair is 1000 times thicker!). Read More
Deployment
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Webb folds origami-style to fit in the Ariane 5 rocket; it unfolds once in space. (How small does it fold up? To about a quarter of its longest dimension so it fits in the 5m wide rocket.) Deployment Video
Operating Temperature
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Webb operates at just a few degrees above absolute zero! (Its operating temperature is under 50K, or -370F.) Video
Wavelengths
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Webb will see the universe in light invisible to human eyes. Though it seems primarily infrared light, it can also see red and gold visible light. (Webb’s wavelength range is 0.6 to 28.5 microns.) Read More
Sensitivity & Resolution
Sensitivity
Webb is so sensitive, it could detect the heat signature of a bumblebee at the distance of the moon, and can see details the size of a US penny at the distance of about 24 miles (40 km). (That's a limiting sensitivity of ~11 nJy and spatial resolution of better than 0.1 arc-secon at 2 microns.) Read More
Exoplanet Atmospheres
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Webb can see water vapor in extrasolar planet atmospheres. (If there were chlorofluorocarbons (CFCs) on an exoplanet, Webb would see them..) Read More
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Webb Key Facts International
The Webb Telescope Key Facts have been translated into more than 40 languages. You can read and share Webb Key Facts language cards and PDFs on our Webb Key Facts International page.

Site Hightlights

Featured Images

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Webb Telescope Final Integration Process

The telescope half of the James Webb Space Telescope next to the sunshield half, during the start of the integration process. Image credit: Northrop Grumman

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Sunshield Deployment Testing

The integrated Webb Telescope clears critical sunshield deployment testing. Technicians successfully performed a critical test on Webb's 5-layer sunshield by fully deploying each of its uniquely sized layers to the same position that they will have while orbiting the Sun a million miles away from Earth.

Featured Video

Time-Lapse Video of Webb's Assembly, and Sunshield Deployment

This time-lapse video reveals NASA's James Webb Space Telescope is now a fully assembled observatory, and is accomplishing large scale deployments and movements that it will perform while in space.

In 2019, NASA's James Webb Space Telescope celebrated the full mechanical and electrical assembly of the world's largest, most powerful space science observatory ever built. Meaning that Webb's two halves have been physically put together and its wiring harnesses and electrical interfaces have been connected.

Following assembly, the Webb team moved on to successfully send deployment and tensioning commands to all five layers of its sunshield, which is designed to protect the observatory's mirrors and scientific instruments from light and heat, primarily from the Sun.

Featured Content

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#jwstArt Webb ART & SCIENCE
Twenty two artists were selected nationwide to attend the James Webb Space Telescope Artist Event at NASA's Goddard Space Flight Center in Greenbelt, Md. This gallery shows their impressions of the Webb Telescope and it's mission.